226  How  to  Distinguish  Viburnum  Barks.  {Am-^1?9h6arm- 
stone-cells,  these  interrupted  bands  being  separated  from  each  other 
radially  by  narrow  medullary  rays,  and  longitudinally  by  broader 
bands  of  soft  bast.  The  presence  of  tannic  matters  in  the  middle 
bark,  in  the  soft  bast  and  in  the  medullary  rays  was  referred  to.  It 
Fig.  /.—Viburnum  opulus.  Bark  of  stem.         folium.    Bark  of  trunk. 
Cross-section.  Longitudinal  section. 
was  shown  in  the  case  ot  V.  prunifolium  that  it  contained,  instead  of 
the  bands  of  bast  fibres,  numerous  groups  of  stone-cells  irregularly 
disposed.  Longitudinal  sections  were  also  shown,  making  clear  the 
points  made— that  these  barks  were  quite  different  in  structure. 
The  statement  was  made  that  it  was  probably  possible  to  distin- 
